自學安卓複習基礎_之九（使用適配器ArrayAdapter來實現listView的CRD）

Android 中適配器有很多，我今天來講講比較常用的ArrayAdapter實現listview的增刪查。
步驟一：創建一個實體類，作爲ListView適配器的適配類型

public class Fruit implements Serializable{

    private String name;
    private int img;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getImg() {
        return img;
    }
    public void setImg(int img) {
        this.img = img;
    }
    public Fruit(String name, int img) {
        this.name = name;
        this.img = img;
    }

}

步驟二：創建兩個layout佈局，一個是listView的子項佈局，一個是listview頁面佈局
list.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >
    <Button 
        android:id="@+id/btn"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="添加一個item"
        />
<ListView 
    android:id="@+id/lv"
    android:layout_height="wrap_content"
    android:layout_width="match_parent"
    ></ListView>
</LinearLayout>

item.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal" >
   <ImageView 
       android:id="@+id/iv"
       android:layout_height="80dp"
       android:layout_width="80dp"
       android:src="@drawable/d"
       />
    <TextView 
        android:id="@+id/tv"
        android:layout_height="80dp"
        android:layout_width="0dp"
        android:layout_weight="1"
        android:text="hahhaha"
        android:gravity="center"
        />

    <Button
        android:id="@+id/btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="刪除" />

</LinearLayout>

步驟三：創建一個自定義的適配器，這個適配器需要繼承ArrayAdapter其泛型指向Fruitt

public class FruitAdapter extends ArrayAdapter<Fruit>{

    private MainActivity mainActivity;
    private int resourceid;
    public FruitAdapter(MainActivity context, int resource, List<Fruit> objects) {
        super(context, resource, objects);
        // TODO Auto-generated constructor stub
        this.mainActivity=context;
        this.resourceid=resource;
    }

    @Override
    public View getView(final int position, View convertView, ViewGroup parent) {
        // TODO Auto-generated method stub
        ViewHolder holder;
        View view;
        if (convertView==null) {
            view=LayoutInflater.from(getContext()).inflate(resourceid, null);
            holder=new ViewHolder();
            holder.iv=(ImageView) view.findViewById(R.id.iv);
            holder.tv=(TextView) view.findViewById(R.id.tv);
            holder.btn=(Button) view.findViewById(R.id.btn);
            view.setTag(holder);
        }else {
            view=convertView;
            holder=(ViewHolder) view.getTag();
        }
        Fruit fruit=getItem(position);
        holder.iv.setImageResource(fruit.getImg());
        holder.tv.setText(fruit.getName());
        holder.btn.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {


                mainActivity.removeIt(position);
                //notifyDataSetChanged();

            }
        });
        return view;


    }
    class ViewHolder{
        private ImageView iv;
        private TextView tv;
        private Button btn;
    }
}

步驟四：完成修改MainActivity的代碼

public class MainActivity extends Activity {

    private List<Fruit> all = new ArrayList<Fruit>();

    private ListView lv;
    private FruitAdapter adapter;
    private Button btn;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);

        setContentView(R.layout.list);
        initData();//初始化水果數據
        lv = (ListView) findViewById(R.id.lv);
        btn = (Button) findViewById(R.id.btn);
        adapter = new FruitAdapter(MainActivity.this, R.layout.item, all);

        lv.setAdapter(adapter);

        btn.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                addItem();
            }
        });
        // initData();

    }

    public void initData() {

        Fruit fruit = new Fruit("a", R.drawable.a);
        all.add(fruit);
        Fruit fruitb = new Fruit("b", R.drawable.b);
        all.add(fruitb);
        Fruit fruitc = new Fruit("c", R.drawable.c);
        all.add(fruitc);
        Fruit fruitd = new Fruit("d", R.drawable.d);
        all.add(fruitd);
        Fruit fruit1 = new Fruit("a", R.drawable.a);
        all.add(fruit1);
        Fruit fruitb2 = new Fruit("b", R.drawable.b);
        all.add(fruitb2);
        Fruit fruitc3 = new Fruit("c", R.drawable.c);
        all.add(fruitc3);
        Fruit fruitd4 = new Fruit("d", R.drawable.d);
        all.add(fruitd4);
        Fruit a = new Fruit("a", R.drawable.a);
        all.add(a);
        Fruit b = new Fruit("a", R.drawable.a);
        all.add(b);
        Fruit c = new Fruit("a", R.drawable.a);
        all.add(c);
        Fruit d = new Fruit("a", R.drawable.a);
        all.add(d);
        Fruit e = new Fruit("a", R.drawable.a);
        all.add(e);

        Fruit f = new Fruit("a", R.drawable.a);
        all.add(f);

    }

    // 在adapter類裏點擊刪除按鈕時調用這個方法
    public void removeIt(int position) {

        all.remove(position);
        adapter.notifyDataSetChanged();

    }

    // 點擊“添加一個item”按鈕時調用這個方法
    public void addItem() {
        Fruit f = new Fruit("新的item", R.drawable.a);

        all.add(0, f);
        // 及時刷新，不然出現不了數據
        adapter.notifyDataSetChanged();
    }

}

步驟五：最後不要忘記在清單文件中註冊MainActivity哦。這樣就完成了簡單的增刪查啦。在getView代碼中，我用了最好的提高listView提升運行效率的方式，代碼在這，大家可以慢慢的去斟酌，感悟就是不是多看，是多敲代碼。如還有不懂可給我留言。